JPH06273103A - Method for measuring outside diameter of cylindrical object - Google Patents

Abstract

PURPOSE:To find a true outside diameter by joining a plurality of measuring errors within an outside measuring range of a detector, finding a calibration curve of the detector and applying a correction value obtained from the calibration curve to an outside diameter measured value of a measurement object of an arbitrary outside diameter. CONSTITUTION:Movement of a frame 4 having fixed an outside diameter measuring device 3 is controlled with a controller 8 and a signal transmitted from the device 3 is data-processed 7. The device 3 is moved up to a position of a calibration gage 6, outside diameter measurement is performed for gages 6 with different outside diameter values respectively and a differences between an outside diameter measured value and the outside diameter value of the gage 6 is plotted for each outside diameter value. Each plotted point is joined with a least square method and a calibration curve can be obtained. A series of data processing such as plotting of measured data and calculation of the calibration curve can be automatically, performed with a computer. Next, a correction value is found from the calibration curve for the outside diameter measured value, applied thereto and a true outside diameter value can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring the outer diameter of a cylindrical object such as a mechanical shaft.

[0002]

2. Description of the Related Art In order to perform the outer diameter of a cylindrical object such as a machine shaft with high accuracy, both a non-contact type and a contact type have been proposed and put into practical use. There is. In particular, a non-contact type outer diameter measuring device using a laser is widely used because of its wide measuring range and high measuring accuracy.

In the non-contact method using a laser, the distance from the reference point at two points facing each other at a known distance so as to sandwich the measurement object to the surface of the measurement object is measured, and the distance between the reference points is set to 2 Method to determine the outer diameter of the measured object by subtracting two distance measurement values, or irradiate the measured object with a laser beam in a band shape and detect the width of the shadowed area of the measured object with the detector on the opposite side of the measured object. There is a method of measuring the outer diameter of the object to be measured. A specific outer diameter measuring method will be described with reference to FIG. 7 by taking the latter as an example.

A laser light projecting portion 3a and a light receiving portion 3b are arranged on both sides of the object to be measured 1 so as to sandwich the object to be measured 1. A laser beam 9 in the form of a spot is scanned from the laser projecting unit 3a onto the object to be measured 1 in parallel and at a constant speed, and is received by a light receiving unit 3b on the opposite side of the object to be measured 1. The received signal is converted into an electric signal and then sent to the outer diameter computing device 7, where the time during which the laser beam 9 is blocked by the measuring object 1 is converted into a length, whereby the outer diameter of the measuring object 1 is calculated. Can be measured. When the traveling direction of the laser light 9 is the X direction and the scanning direction of the laser light 9 is the Y direction, the angle formed by the X direction and the Y direction is 90 degrees.

[0005]

In the above outer diameter measuring method, a measurement error occurs due to the characteristics of the optical components used inside the detector, component mounting errors, or calculation errors during signal processing. As shown in FIG. 8, the measurement error often does not become the same value for each outer diameter value within the measurement range.

Since it is necessary to measure the outer diameter of a machine shaft or the like with extremely high accuracy, it is usually necessary to measure the outer diameter with a calibration gauge having an outer diameter value substantially equal to the outer diameter of the object to be measured before measuring the outer diameter. In many cases, the outer diameter of the object to be measured is measured after performing the diameter measurement to calibrate the zero point of the detector. However, according to this method, it is necessary to prepare a calibration gauge having substantially the same outer diameter value as that of the object to be measured before measurement, which requires a lot of labor for preparation. Further, when the measured object and the calibration gauge have different outer diameter values, the zero point is not completely calibrated, which causes a measurement error of the outer diameter, which is a problem.

[0007]

The method of the present invention for this purpose is a method for measuring the outer diameter of an arbitrary position in the axial direction of a cylindrical object to be measured, before measuring the outer diameter of the object. The measurement error for each outer diameter value of the detector is obtained with a plurality of calibration gauges having known diameter values and different outer diameter values, and the plurality of measurement errors are measured for the outer diameter of the detector. The calibration curve of the detector is obtained by connecting in the range, and the true outer diameter value is obtained by adding the correction amount obtained from the calibration curve to the outer diameter measurement value of the measurement object of an arbitrary outer diameter. is there.

Generally, in an optical outer diameter measuring device or the like, the outer diameter measurement error continuously changes with the change of the outer diameter value within the measuring range. This is because the error generation factor of the outer diameter measuring device is due to the characteristics of the optical components used inside the detector, component mounting error,
Or it is due to calculation error at the time of signal processing,
This is because each does not occur only at a local position within the measurement range.

Therefore, prior to measuring the outer diameter of the object to be measured,
Within the measurement range, the error amount of the measuring instrument is calculated discretely in advance for different outer diameter values within the measurement range, and the curve connecting the error amounts for these discrete outer diameter values is calculated. It is possible to estimate the error of the measuring device over the entire range. If the estimated error value thus obtained is used as the calibration amount for the outer diameter value of the object to be measured, the outer diameter can be measured with high accuracy without being affected by the error of the measuring instrument.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing a state in which an outer diameter of a mechanical shaft is measured in an example. The cylindrical object 1 is placed horizontally while being supported by the support mechanism 2 from below. The outer diameter measuring device 3 is attached to a gate-shaped stand 4 so as to sandwich the measurement object 1, and a rail 5 is provided between the calibration gauge 6 and the measurement object 1 arranged on the same axis as the measurement object 1. Can be moved, and the outer diameter values of both the measurement object 1 and the calibration gauge 6 can be measured.
The movement of the gantry 4 to which the outer diameter measuring device 3 is attached is controlled by the controller 8. Further, the signal from the outer diameter measuring device 3 is processed by the data processing device 7.

FIG. 2A is a diagram showing the positional relationship between the outer diameter measuring device 3 and the calibration gauge 6. The laser projecting portion 3a and the light receiving portion 3b of the outer diameter measuring device 3 are arranged so as to sandwich the calibration gauge 6. The calibration gauge 6 comprises a plurality of cylinders having different outer diameters and arranged concentrically as shown in FIG. 2 (b). Each outer diameter value of the calibration gauge 6 is precisely measured in advance by another method. The calibration gauge 6 is the measurement object 1.
In the same manner as the above, the axis is arranged so as to be perpendicular to the laser projecting direction and the scanning direction.

FIG. 3 is a plot of the results of measuring the outer diameter of calibration gauges 6 of various sizes. The horizontal axis represents the outer diameter of the calibration gauge, and the vertical axis represents the difference between the measured outer diameter and the outer diameter of the calibration gauge. When the points in FIG. 3 are continuously connected by performing a calculation such as the least square method, as shown in FIG. 4, the error characteristic within the measuring range of the outer diameter measuring device, that is, the calibration of the outer diameter measuring device is performed. A curve can be obtained. When measuring the outer diameter of the measurement object, as shown in FIG. 5, after the outer diameter is measured, a correction amount corresponding to the outer diameter value to be measured may be added to the measured value.

FIG. 6 shows a flow chart of the measuring operation in this embodiment. The outer diameter measuring device 3 is moved to the position of the calibration gauge 6. For calibration gauges 6 with different outer diameter values,
Measure the outer diameter of each. The difference between the outer diameter measurement and the outer diameter value of the calibration gauge is plotted for each outer diameter value. A calibration curve is obtained by connecting the plotted points by a method such as the least square method. A series of data processing such as plotting of measurement data and calculation of a calibration curve can be automatically executed by using a computer. Next, the outer diameter measuring device is moved to the measurement object position. Measure the outer diameter of the object to be measured. A correction amount is obtained from the calibration curve for the outer diameter measurement value, and the true outer diameter value is obtained in addition to the outer diameter measurement value.

According to the present invention, it is possible to obtain the correction amount of the entire area of the measuring range of the outer diameter measuring device from the calibration curve only by performing the outer diameter measurement in advance for a plurality of calibration gauges. , It is not necessary to prepare a calibration gauge with the same outer diameter value as that of the object to be measured, simplifying calibration work and eliminating the measurement error that occurs when there is no calibration gauge with the same outer diameter value as the object to be measured. You can

For example, when measuring the outer diameter of a machine shaft having an outer diameter of 200 mm with a laser outer diameter measuring device, the outer diameter measuring error is about 30 μm when the present invention is not used. 50mm, 100mm, 150mm, 200
As a result of calibrating the detector by performing outer diameter measurement in advance for mm, 250 mm, and 300 mm calibration gauges, the measurement error was reduced to 10 μm or less, and highly accurate outer diameter measurement became possible.・

[0016]

By applying the present invention to the outer diameter measurement of a cylindrical object such as a mechanical shaft, the measurement error of the detector, which has been a problem when using the outer diameter measuring instrument, is significantly reduced. As a result, the accuracy of the measurement can be improved, and the calibration work of the detector before the measurement can be easily and accurately performed.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example in which the present invention is applied to measurement of an outer diameter of a mechanical shaft.

FIG. 2A is a diagram showing a positional relationship between an outer diameter measuring device and a calibration gauge. FIG. 6B is a diagram in which cylinders having different outer diameters are arranged concentrically.

FIG. 3 is a diagram showing a relationship between an outer diameter value of a calibration gauge and a difference between an outer diameter measurement value and a calibration gauge outer diameter value.

FIG. 4 is a diagram showing a calibration curve of an outer diameter measuring device.

5 is a curve diagram when a correction amount is added to FIG.

FIG. 6 is a flowchart of a measurement operation in the example.

FIG. 7 is an explanatory diagram of a conventional outer diameter measuring method.

FIG. 8 is an explanatory diagram of a measurement error by the method of FIG.

Claims (1)

[Claims] 1. A method for measuring an outer diameter at an arbitrary position in the axial direction of a cylindrical measurement object, wherein the outer diameter value is known and the outer diameter value is known before the outer diameter measurement is performed on the measurement object. The measurement error for each outer diameter value of the detector is obtained with a plurality of different calibration gauges, and the calibration curve of the detector is obtained by connecting the plurality of measurement errors within the outer diameter measurement range of the detector. An outer diameter measuring method, wherein the true outer diameter value is obtained by adding the correction amount obtained from the calibration curve to the outer diameter measurement value of a measurement object having an arbitrary outer diameter.